1. Field of the Invention
The invention relates to an improved flashing for roof-top vent pipes, comprising a thermoplastic hard base and an elastomeric rain collar. More specifically, the invention relates to an improved manner of connecting the hard base and rain collar together to form the completed flashing.
2. Brief Description of the Prior Art
Two-piece roof vent flashings are known. For example, British Patent 1,310,003 to BAMBROUGH shows a two-piece roof vent flashing, comprising an aluminum base element with a neoprene collar. The BAMBROUGH collar is connected to the aluminum base either through various mechanical connections, adhesives, or frictional attachments, depending on the particular embodiment. LOGSDON '347 (U.S. Pat. No. 4,160,347) describes a two-piece roof vent flashing comprising a base housing with a sealing collar. The sealing collar is mated with the base housing, and is mechanically held in position by a series of holding flanges on the interior wall of the base housing. LOGSDON '058 (U.S. Pat. No. 4,264,058) shows a two-piece roof flashing structure comprising a hard base and an elastomeric sealing collar. The sealing collar is molded directly onto annular supports, with a series of holes positioned in the inner annular support. During the molding process, material from the collar passes into holes in the inner annular support, thus creating a positive mechanical lock between the collar and base.
KIFER (U.S. Pat. No. 4,526,407) discloses an elastomeric sealing collar connected to a thermoplastic hard base. In KIFER, the sealing collar is molded to a flange on the hard base. The flange has a series of holes therethrough, so that a series of positive mechanical closed-loops are created between the hard base and sealing collar when the sealing collar is molded. HASTY (U.S. Pat. No. 4,864,782) discloses a thermoplastic hard base and an elastomeric sealing collar molded directly to a thermoplastic hard base. In HASTY, the flange has several holes therethrough, allowing the elastomeric material of the collar to pass through the holes during the collar's molding process. Thus, a series of positive mechanical connections are created between the hard base and sealing collar.
Prior art roof flashings involving thermoplastic to thermoplastic construction have relied on positive mechanical connections to maintain the two-part flashings together. One method in the prior art for creating a positive mechanical connection involves creating a flange on the base element, but with the flange having several holes of substantial size, as in HASTY and KIFER. These holes allow the elastomeric material of the collar to pass through the flange during the collar's molding process, thus creating a series of positive mechanical connections between the collar and the base element.
Several problems are created by the presence of holes in the flange. First, the holes necessarily compromise the structural integrity of the flange, increasing the likelihood of structural failure. The holes decrease the minimum path that water must follow to penetrate the flashing along the seam between the collar and the base element. Additionally, the perforated flanges increase the wastage resulting from molding the base element and from molding the collar onto the base element.
Solid flanges have been known in the art. For example, a roof flashing manufactured by the Never-Leak Company of Memphis, Tenn., has a solid flange. However, that flange is conical and relatively small in width.
Previous solid flange designs have been prone to failure of the seam between the flange and the collar, allowing water to penetrate. To compensate for anticipated seam failures, previous solid flanges have been generally conical in shape, with the conical flange sloping outwardly away from the center opening of the base element. Thus, water is diverted away from the center opening.